This invention relates to a method and an apparatus for erecting building structures or the like, having a substantially dome-like shape, as well as to a structure thus obtained.
As is known, dome buildings constitute, by virtue of their very shape, specially useful constructions both from an aesthetic standpoint, since they merge easily and pleasantly into the landscape, and from a structural point of view, because they may be formed as a monolithic self-supporting diaphragm which is effectively capable of withstanding stresses and requires, for its construction, a reduced amount of material with respect to more conventional building designs.
However, domed buildings have the disadvantage of being difficult to erect since, if produced with the usual techniques as employed for conventional buildings, they require a complex falsework of correspondingly domed shape for casting the concrete material. These difficulties have been only partly overcome by adopting a support for concrete material casting which comprises an inflatable bag or balloon having the same shape as the dome to be erected. This balloon, owing to the ease wherewith it may be inflated and positioned, represented a simplification in dome building structure forming, for it did away with the necessity for inner dome scaffolding, although it still required outer scaffolding. It is in fact apparent that, even if said inflatable bag can support and hold in shape the concrete material, it cannot provide adequate support, without undergoing considerable deformation, for the weight of the concrete spraying personnel and machines, thereby the outer scaffolding is to be provided.
Such shortcomings have been effectively and uniquely obviated through previous studies and patents which teach the erection of domed building structures by casting the concrete material and positioning the related reinforcement on the flat, directly at ground level, over a membrane which may be then inflated to take a final shape at least in part matching or in agreement with the structure to be erected. In that manner, all of the material was distributed at ground level and the outer scaffolding became unnecessary. Furthermore, with that method, other substantial advantages were secured such as a remarkably shorter erecting time for the entire building structure and a more easily distributed concrete material, since all the operations involved were performed substantially on the ground and required no spraying machines or pumps of specially high power in order to spread the concrete material.
It is thanks to such advantages and to its uniqueness with respect to prior art techniques that the cited method has met with worldwide acceptance. In time, however, ever growing requisites of convenience, size and economy in building structures have led to the requirement for a further evolution of the cited method. In particular, the need is now felt for a more economical erection procedure for such dome-like building structures, as well as of arriving at domes of larger diameters. In fact, when a dome with a diameter of 40 meters (131 feet) up is to be erected, it is necessary to cast, in a short time, onto said elastic membrane, a large amount of concrete, such as to complete the covering of the whole membrane to the desired thickness before the concrete casting has a chance to lose the fluidity required to absorb the deformation imparted thereto by the membrane as it is inflated. It has been found in actual practice, that for domes with diameters equal to or exceeding 40 meters (131 feet), it is particularly difficult to complete the casting operation quickly enough, especially at far out sites or sites lacking casting facilities.
In situations such as mentioned above, the problem is encountered of how to erect large diameter domes while retaining the essential advantage of requiring no prearranged supporting falsework, and while improving the economy and constructional accuracy of the resulting dome.